1. Field of the Invention
The present invention concerns a videorecorder with which it is possible to add further information to information already recorded on a magnetic tape. As a general rule this is done in such sections of the recording tracks that are not correlated with visible lines.
2. Description of the Prior Art
When information has to be added to information already recorded on a magnetic tape, one has to keep on switching from a playback mode to a recording mode and viceversa. In the playback mode of operation one ascertains when a horizontal synchronization pulse occurs to indicate the beginning of the recording section for a line. The equipment is then switched to the recording mode for a pregiven period of time. Shortly before one can expect the next horizontal synchronization pulse, the equipment is switched back to the playback mode, thereby making it possible to detect this pulse. This switching is associated with signal disturbances that could lead to playback errors when the added information has to be read on a subsequent occasion. With a view to avoiding these reading errors to the greatest possible extent, it is a common practice not to commence the recording of the added data immediately after the switching, but to record at first only the unmodulated FM carrier, subsequently modulating this carrier with data recording signals after the lapse of a waiting period of the order of 20-30 .mu.sec. The disturbances caused when switching from the playback mode to the recording mode will not therefore have any effect when the information is subsequently played back. But there is the compensating drawback that considerable recording capacity is lost.
The above remarks make it clear that for considerable time past there has existed the problem of defining a videorecorder that would make it possible to record information on a tape that already carries other information and to do this in a manner reasonably free of disturbances.